Reactive oxygen species (ROS) are implicated in a variety of biological functions. For example, intracellular changes in ROS can influence cell signaling by thiol oxidation within target proteins, resulting in changes that affect the structure-function properties of the proteins. Oxidation by ROS has also been attributed to activating kinases and inhibiting phosphatases, leading to enhancement of phosphorylation cascades. Conformational changes due to oxidation by ROS can also result in changes in protein stability, protein-protein and protein-DNA interactions, and subcellular localization. Redox regulation, in which ROS play a role, has been attributed to various signaling pathways and may affect cellular responses such as transcription regulation, proliferation, migration, metabolism, survival and inflammatory response.